Nitrogen and phosphorus pollution alter the mutual relationship between corals and algae

phosphorus pollution change the relationship between the pistillata and the algae living inside its tissues, a recent study has found. The researchers say the pollutants, mainly from urban and agricultural discharges, affect algae photosynthesis and the essential transfer of carbon from algae to the coral.

Nitrogen and phosphorus pollution change the relationship between the tropical coral Stylophora pistillata and the algae living inside its tissues, a recent study has found. The researchers say the pollutants, mainly from urban and agricultural discharges, affect algae photosynthesis and the essential transfer of carbon from algae to the coral.

Algae live inside many reef-building corals, a symbiotic relationship which benefits both the algae and the corals. The algae are protected by the coral and use its waste products for their photosynthesis and in turn the coral uses photosynthetic by-products, particularly carbon, to respire, reproduce and build coral skeletons.

Anything which disturbs this finely balanced relationship can impair the healthy development of the coral. Seawater polluted by excess nitrogen and phosphorus, mainly from urban and agricultural discharges, may affect the nitrogen to phosphorus balance and upset the tight algae—coral relationship.

This study focused on how different ratios of nitrogen and phosphorus affected the metabolism of the tropical coral Stylophora pistillata colonised with Symbiodinium algae species.

The researchers suspended small coral fragments in tanks, through which seawater containing added phosphorus and various forms of nitrogen was circulated. Control tanks were provided with natural seawater containing low levels of nitrogen (N) and phosphorus (P) (0.5 μM N and 0.05 μM P). Two further nutritional treatments were provided with natural seawater enriched with 2.5 μM N, in the form of ammonium or nitrate. A third treatment contained seawater enriched with 1 μM P and 2.5 μM ammonium.

After three weeks under these nutritional treatments, the researchers took samples from each tank and measured algal photosynthesis, chlorophyll, and algal content as well as rates of respiration of coral and algae and coral calcification (skeleton building).

Other samples were immersed in beakers using the same experimental conditions they were grown in, plus the heavy isotope of carbon, 13C, as a tracer. They measured the carbon incorporation rate in the algae material and coral tissues and then combined these measurements in a model to estimate the amount of carbon transferred from algae to coral.

Overall, they found the relative amounts of nitrogen and phosphorus, as well as the form of nitrogen, affected their mutual functioning and the transfer of carbon from algae to coral in different ways.

For instance, nitrogen enhancement in either the ammonium or nitrate form doubled algae growth compared with control conditions. However, higher levels of carbon were only transferred from algae to coral hosts under ammonium enrichment. Coral calcification rates were consequently increased under enriched ammonium conditions, but not under nitrate enrichment.

It costs the algae extra energy to utilise nitrate, as it must first be converted to the ammonium form, before being combined with carbon so it can be used. The researchers suggest this negatively affects photosynthesis and consequently coral calcification. As ammonium is a form of nitrogen mainly found in fish excretions, the researchers suggest that supporting fish colonies above coral reefs could enhance coral growth.

A phosphorus/ammonium-enriched environment also unbalanced the coral—algae relationship. The researchers found that the algae multiplied at the expense of the coral hosts by keeping more of the photosynthetic products for their own use.

This study was carried out in the laboratory on one coral species under normal growth conditions (25°C), and cannot be generalised to other coral species living in different environments. The results nevertheless advance knowledge of how nutrient pollution affects coral reef ecosystems, which is useful for policymakers assessing risks to coral reefs from human activities.

Related articles

On July 14, 2016, the U.S. Department of Energy (DOE), announced $15 million in funding for three projects that will work to improve algal biomass yields to reduce production costs of algae-based biofuels and bioproducts. The projects include Global Algae Innovations (San Diego, California), Algenol Biotech LLC (Ft. Myers, Florida), and MicroBio Engineering, Inc. (San Luis Obispo, California). These projects will coordinate algae strain improvements through harvesting, dewatering, and downstream processing,...

As part of the Clearwater PMPC project, 2 MPC Buoys were deployed in the Skrzyneckie Małe Lake to test the performance of this unique technology.The Challenge: Control and Monitor Toxic Algal BloomsThe ClearWaterPMPC project was initiated by LG Sound and funded by "Research for SMEs" within the EU 7th Framework Programme. The goal of the ClearWaterPMPC (Predicting, Monitoring,Preventing, and Controlling) project was to develop an environmentally friendly technology to prevent growth of blue-green algae in...

Since February 2016, Salmon farms in Chile have been suffering from an intensive Harmful Algal Bloom (HAB) which is causing massive numbers of salmon deaths. Ultrasonic technology combined with algae detection could be the solution for an industry facing economic losses totaling millions. Currently the Dutch algae control company, LG Sonic, is discussing the implementation of ultrasonic technology with the salmon industry in order to control the algal blooms.
Algal Blooms Cost Chile’s Salmon Farms $800m
Tox...

The Utility:The Santa Clara Valley Water District (the District) manages an integrated water resources system that includes the supply of clean, safe water, flood protection, and stewardship of streams on behalf of Santa Clara County`s 1.8 million residents. The district effectively manages 10 dams and surface water reservoirs, three water treatment plants, an advanced recycled water purification center, a state-of-the-art water quality laboratory, nearly 400 acres (162 hectares) of groundwater recharge ponds,...

On October 2, 2015, at the 2015 Algae Biomass Organization Summit, the Algae Foundation announced a U.S. Department of Energy (DOE) funded education initiative to enhance algae workforce development. The Algae Foundation is a non-profit organization committed to expanding the algae industry though research, education, and outreach, and plays an important part in advancing the bioeconomy beyond ethanol. The DOE-funded initiative will focus on developing a college degree in algal cultivation technologies that will...

Customer comments

No comments were found for Nitrogen and phosphorus pollution alter the mutual relationship between corals and algae. Be the first to comment!